Artillery fire control system



April 11, 1967 M. F. THOMPSON Filed June 24, 1965 ARTILLERY FIRE CONTROLSYSTEM 4 Sheets-Sheet l r- -I I I I I I 1 2| I ADDRESS MESSAGE I I I IAZ ooome 059 I I I CONTROL CONTROL I I CONSOLE UNIT I6 23 EL' -fif I I 2I I MV use 22 I TRANSMITTER I I IFJ I 53 24 I I I so RECEIVER I I Q G I:I I MESSAGE I CODING I I I CONTROL ,ee 25 I BATTERY UN"- I COMMAND f IPOST 2 I e FILT' I L. .I

I I I ,-46 I GUN u ER MESSAGE fI I N MB I 08 c I I comm; 3| I l ICONTROL f I I osc I I 47 TRANSMITTER I l ERROR DETECTOR ;E52 RECENER III I 32 I f I FILT I ADDRESS DECODER I i 2 7 H FILT 33 I i I sunPOSITION 2 SIMILAR T0 GUN POSITION II I2 M FIG. I

ZNVENTOR. MALCOLM F. THOMPSON ATTORNEY April 11, 1967 Filed June 24,1965 M. F. THOMPSON ARTILLERY FIRE CONTROL SYSTEM GUNTAIL L v I s7 72 IF|G.5 I

4 Sheets-Sheet 2 as 6l 75 I 82 N' 4 7s INVENTOR. MALCOLM F. THOMPSON BY1 I ATTORNEY April 1967 M. F. THOMPSON ARTILLERY FIRE CONTROL SYSTEM 4Sheets-Sheet 5 Filed June 24, 1965 FIG. 4

INVENTOR.

MALCOLM F. THOMPSON JMM ATTORNEY April '11, 1967 M. F. THOMPSONARTILLERY FIRE CONTROL SYSTEM 4 Sheets-Sheet 4 Filed June 24, 1965 FIG.6

INVENTOR. MALCOLM F. THOMPSON ATTORNEY United States Patent ()fifice3,313,209 ARTHJLERY FIRE CONTROL SYSTEM Malcolm F. Thompson, Santa Ana,Califi, assignor to North American Aviation, Inc. Filed June 24, 1965,Ser. No. 466,613 3 Claims. (CI. 89-41) This invention relates to a firecontrol system for artillery and more specifically to a system for theautomatic transmission of fire control data to remote gun positions, andautomatic transmission of messages to the battery command post fromremote gun positions indicating that the guns have been properly laid.

The accurate transmission of fire control commands between the batteryexecutive at a command post and gun crews at remote gun positions isdesirable for the correct laying of the guns and quick verification bythe executive that the guns have been properly laid. It has beendiscovered that the operations involved could be executed moreefficiently with minor modifications to existing equipment including atwo-wire telephone line for communications between the battery commandpost and all of the remote gun positions.

Present day field artillery weapons are optically sited in azimuth andlaid in elevation from a bubble level. Voice commands have been employedto accomplish this using field telephones to reach remote gun positions.The possibility of error exists in such voice communications, both inthe transmission and in the interpretation of the commands, due to thehuman element involved. Faster and more accurate fire control could beestablished by automatic transmission of fire control data to the guns,and transmission to the command post of verification that the guns havebeen properly laid.

Another problem encountered in the past relates to maintaining anoptimum high angle trajectory for varying ranges by varying the powdercharge for various ranges. Faster reaction time and a greater firingrate could be maintained if fixed ammunition could be employed forallranges with optimum high angle trajectory for each. If a variable muzzlevelocity could be obtained with fixed ammunition, all gun layingcommands could be quickly transmitted in terms of azimuth, elevation andmuzzle velocity in such a Way as to allow each variable to be similarlyadjusted until all variable elements of the gun correspond to thecommands received.

An object of this invention is to provide a system for the automatictransmission of fire control commands to a gun at a remote position froma command post and for automatic verification at the command post thatthe gun has been properly laid.

Another object of the invention is to provide automatic transmission offire control commands to a plurality of guns at remote positions andautomatic verification at the command post that the individual guns havebeen properly laid.

Another object is to provide automatic transmission of fire controlcommands to a selected one of a plurality of guns and automaticverification that the gun selected has been properly laid.

Another object is to provide automatic transmission of individual firecontrol commands to selected ones of a plurality of guns and automaticverification that the guns selected have been properly laid.

Still another object is to provide a system for the automatictransmisison of fire control data including muzzle velocity andautomatic verification that the gun has been properly laid in allrespects including the muzzle velocity.

A more specific object of the invention is to provide a system for theautomatic transmission of fire control commands to a gun at a remoteposition and automatic 3,313,269 Patented Apr. Ill, 1967 interpretationand comparison of the commands with compliance therewith, and automaticindication of the compliance to allow the gun laying crew to so adjustthe variables of the gun as to provide compliance with the fire controlcommands and as a further object to automatically transmit to thecommand post a message that the gun has been properly laid when each ofthe variables of the gun has been adjusted to the position indicated bythe gun laying command.

These and other objects of the invention are achieved in a system inwhich fire control commands for remote gun positions are either manuallyentered or calculated by a computer at a battery command post, andautomatically transmitted in digital form to the guns over a singletwo-Wire communication channel. The gun laying command message for agiven gun consists of the gun address, azimuth, elevation and, ifdesired, muzzle velocity. Each message is transmitted over the two-wirecommunication channel to all remote gun positions where the addressportion is decoded. Only that gun being addressed responds to theaddress portion of the message to enable a comparator to receive the gunlaying commands which follow for comparison with the azimuth, elevationand, if required, muzzle velocity setting of the gun. The comparatorvisually displays to the gun crew when the gun setting is too high, toolow or on target with respect to elevation and, if required, muzzlevelocity, and too far right, too far left or on target with respect toazimuth. A coordinate converter is provided to convert gun deflectionand elevation to true azimuth and elevation for direct comparison withthe azimuth and elevation commands.

When the gun is properly set with respect to all vari ables, thecomparator causes a message to be transmitted to the battery commandpost. The message comprises the address of the gun; its meaning that thegun has been properly laid is implied. The command post receives themessage and displays it. If more than one gun is being employed, thebattery executive may withhold the command to fire until all of the gunshave been properly laid. He may however issue the command to fire theguns individually as verification is received that the guns have beenproperly laid. This verification is provided by visual display devices,one for each gun, energized individually when the guns transmit messagesindicating that they have been properly laid.

Other objects and advantages of the invention will become apparent fromthe following description with reference to the drawings in which:

FIGURE 1 is a block diagram of an illustrative embodiment of theinvention;

FIGURE 2 illustrates the manner in which the gun barrel elevation axismay be translated to a parallel position which intercepts the deflectionaxis of the gun;

FIGURE 3 illustrates a side view, partly in section, of a device forconverting gun elevation and deflection with respect to the mutuallyperpendicular gun trunnion and gun deflection axis to true elevation andazimuth;

FIGURE 4 is a top view of the device of FIGURE 3;

FIGURE 5 illustrates the manner in which the device of FIGURE 3 isemployed to provide a true horizontal and vertical reference for a giventrunnion tilt angle;

FIGURE 6 shows in cross-section a variable porting arrangement foradjusting the muzzle velocity of a gun using fixed ammunition; and

FIGURE 7 is a cross-section taken along the line 7-7 of FIGURE 6.

The general system organization of the present inven tion is illustratedschematically in FIGURE 1 as comprising a battery command post 10 and aplurality of gun positions 11 and 12, all of which are connected to apair of field telephone wires 13. Since all of the gun positions aresimilar, only one has been illustrated schematically in block diagramform. The second gun position 1 2 is identical to the gun position 11except as will be explained hereinafter, adapted to respond to adifferent address code. Additional gun positions may be similarlyconnected to the telephone wires 13.

The battery command post and gun positions transmit and receive over thesingle pair of field telephone wires 13. The gun laying commands aretransmitted from the battery command post to all of the gun positions asbinary coded messages. A given message sent from the battery commandpost to a particular gun position, such as the gun position 11, consistsof at least 13 binarycoded-decimal (BCD) characters. The first BODcharacter of the message is the numerical address of the gun position.

An artillery fire unit usually includes only six gun positions so that asingle BCD character is sufficient to uniquely address each of the gunpositions. However, if a larger number of gun positions are to becontrolled by the same battery command post, the address portion of themessage may be expanded to more than one BCD character.

The address of the gun position is followed by the azimuth and elevationcommand, and if desired, a muzzle velocity command, each of whichcomprises four BCD characters. The message is transmitted seriallystarting with the least significant BOD character of the gun address andconcluding with the most significant BCD character of the muzzlevelocity command. If parity error detection is included, each message orportion thereof, may be terminated by a binary parity digit in a mannerwell known to those skilled in the art.

When it is desired to send a message from the battery command post, aninitiate switch 15 is actuated to cause a signal to be sent to a messagecoding control unit 16 which sequences the transmission of the messagein the order indicated, namely address code followed by commands forazimuth, elevation, and if included, muzzle velocity. The message to betransmitted is composed at a console 17, either manually by the batteryexecutive officer on instructions from a fire direction center (notshown), or by a computer included in the console which receives its datafrom the fire direction center.

The message coding control unit 16 includes means for producing a seriesof coded binary digits and synchronizing signals. These signals areapplied to a pair of oscillators 21 and 22 that control the output of atransmitterreceiver 23 which preferably comprises a hybrid transformerof the type employed in two-wire telephone communications, with oneamplifier between the oscillators 21 and 22 and the hybrid transformerfor amplifying transmitted messages, and another amplifier between thehybrid transformer and a pair of selected bandpass filters 24 and 25 foramplifying messages received over the telephone lines 13. Thus thehybrid transformer having its two-wire output connected to the telephonelines 13 will allow two way communication between the battery commandpost and any one of the gun positions without the battery command postreceiving its own message.

As the message coding control unit 16 affects the transmission of themessage, it routes digits of one binary value to one oscillator anddigits of the other binary value to the other oscillator, such as thebinary-zero digits to the oscillator 21 and the binary-one digits to theoscillator 22. Each binary digit received by the oscillators 2 1 and 22will trigger the associated oscillator to cause it to transmit a signalof one frequency or the other of the two frequencies f and f selectedfor the oscillators 21 and 22. This frequency-shift coding of themessage is preferred, although generally more prodigal of bandwidth thanphase-shift modulation, in order to provide a less complex, andtherefore less expensive, transmitterreceiver 23. However, it should beunderstood that any pulse code communication system known may beemployed such as phase-shift or amplitude modulation systems. Thus eachdigit transmitted consists of a short pulse of one or the other of thetwo frequencies and f each for a predetermined length of time. Thesynchronizing signals may consist of longer pulses of a selected one ofthe frequencies f and f or combinations thereof.

When the gun crew at the gun position being addressed has complied withall commands of the message the gun position automatically transmits amessage over the telephone lines 13 to the battery command post. Thatmessage consists of simply the address of the transmitting gun position,it being understood that the transmission of gun position address to thecommand post means that the gun has been properly laid as commanded.However, the message may consist of the gun position address and one ormore binary coded words. In any case, the message is received over thetransmitter-receiver 23 and filters 24 and 25 which identify the binarydigits zero and one, respectively.

The message decoding control 26 receives the binary digits from thefilters 24 and 25 over separate lines and combines them for decoding.Once the message has been decoded, a visual display indicatorcorresponding to that gun position is energized. For instance, if thegun position 11 is designated Gun No. l, a gun laying command receivedand executed by that gun position causes its address code to betransmitted to the battery command post where it is decoded to energizeindicator 1. Once the battery executive officer sees that the visualdisplay indicator 1 has been energized, he may issue the order to fireGun No. 1 by voice communication over the telephone lines 13.

At each gun position, the message transmitted by the battery commandpost is received over a transmitterreceiver 31 identical to thetransmitter-receiver 23 of the battery command post 19. A pair offilters 32 and 33 distinguish the binary digits of the received messagein the same manner as filters 24 and 25 of the command post. As notedhereinbefore, the first portion or word of the message is abinary-coded-decimal number identifying the gun being addressed. Anaddress decoder 34 receives the binary digits from the filters 32 and 33and determines whether that gun position is being addressed.Accordingly, the address decoder 34 is conditioned to detect only theaddress code assigned to its gun position. That may be readilyaccomplished by a four-bit shift register adapted to receive the binarydigits from the filters 32 and 33 so that when the entirebinary-coded-decimal number for the gun position has been received, thecontents of the shift register may be examined in parallel through adiode decoding matrix programmed through a plugboard (not shown) toidentify the BCD number. Alternatively, the decoding function may becarried out by serially comparing the digits of the received BCD numberwith a stored number as by effectively subtracting the received numberfrom the stored number. To facilitate that, the stored number may be inthe 2s complement form so that the subtraction may be carried out by aserial binary adder; the difference is then immediately tested todetermine whether it is zero.

Once the address portion of the message has been identified by theaddress decoder 34, it transmits a control signal to a comparator 35which is then enabled to receive the remaining portion of the messageconsisting of the azimuth, elevation, and if included, muzzle velocitycommands for the gun. The individual commands received by the comparator35 are compared with the actual settings of the gun read out in digitalform through binarycoded-decimal converters or encoders 41, 42 and 43.The comparator 35 may be attached to the gun in a convenient locationwith three error displays 36, 37 and 38 so mounted as to be readilyviewed by members of the gun crew. For instance, the elevation settingof the gun is read out through the encoder 41 and compared with theelevation command. If the elevation setting is greater than theelevation command, a high or H indication is displayed to the crewmember who trains the gun in elevation. The display device 37 willsimilarly indicate when the elevation setting is less than the commandby displaying a low or L indication. When the elevation setting is equalto the elevation command, the indicator 37 displays an on target or Oindication. The display devices 36 and 38 perform similar functionsexcept that the display device 36 associated with the azimuth setting ofthe gun will display a left or L indication when the gun deflectionsetting is greater than the azimuth command.

The comparator compares the gun laying commands in the order receivedwith the settings read out through the encoders 41, 42 and 43. As eachcomparison is made, the corresponding error display device is set toindicate whether the gun is laid too high (or too far right) or too low(or too far left). The gun crew then adjusts the gun accordingly. In themeantime, the comparator will not transmit a signal to a message codingcontrol unit 45. After a predetermined delay period of less thanone'second, the battery command post automatically retransmits the samemessage. I

When the battery command post is communicating with only one gun, itretransmits the same message until the comparator 35 at that gunposition being addressed determines that the gun is properly laid inazimuth, elevation, and if required, muzzle velocity. Once the gun isproperly laid, the indicators 36, 37, 38 announce that to the gun crewand the comparator transmits a signal to the message coding control unit45 which then transmits a message indicating the gun has been properlylaid. Transmission of the on target message is accomplished by frequencyshift coding through oscillators 46 and 47 in the same manner thatmessages are transmitted by the battery command post.

With a communication pulse rate of 1000 binary digits per second, acomplete message from the battery command post to a gun positionincluding azimuth, elevation and muzzle velocity commands would requireless than 60 milliseconds. If the same amount of time is allotted for areply from the gun position, the message coding control unit 16 at thebattery command post may automatically retransmit the message every 120milliseconds, or 8 times per second. Once the gun has been properly laidand an on target message has been received by the message decodingcontrol unit 26, a signal is transmitted over a line 50 to the messagecoding control unit 16 to terminate transmission of the message.

If the battery command post is transmitting the same gun laying commandsto all of the guns, for example all six guns in the unit assigned to thebattery command post, the message coding control unit 16 will cyclethrough the individual messages for all of the guns pausing after eachmessage transmission to receive an on target message indicating that thegun just addressed is properly laid. In that manner, the message codingcontrol unit 16 will cyclically transmit all of the messages until allguns are properly laid. For that mode of operation, the message decodingcontrol unit 26 will not transmit a signal over the line 50 to stoptransmission of messages until an on target message has been receivedfrom each of the guns and all of the visual indicators 1 through 6 atthe battery command post 10 have been energized.

If parity error detection, or any other system of error detection isprovided, an error detector 52 may be connected to both the addressdecoder 34 and the comparator 35 at the gun position 11 in order thaterror detection of both the address code and the azimuth, elevation andmuzzle velocity commands may be checked." If an error is detected, theerror detector 52 will cause the message coding control unit 45 totransmit only an error message immediately after transmission from thebattery command post 10 to the gun position 11 has been completed. Anyerror message received by the transmitter-receiver 23 of the batterycommand post 10 is then decoded by the message decoding control unit 26which transmits a signal over a line 53 to cause the last message to beretransmitted.

The azimuth and elevation commands transmitted to a gun position are interms of true azimuth and true elevation. If the gun is level so thatthe gun trunnion is horizontal and the gun deflection axis is vertical,the azimuth and elevation encoders 41 and 42 may be read and directlycompared with the azimuth and elevation commands. However, as is usuallythe case, the gun is not level. Therefore in order to be able to make adirect comparison of azimuth and elevation commands with the output ofthe encoders 41 and 42, a coodinate converter is required between thegun and the encoders 41 and 42 to eliminate the error which wouldotherwise appear both in azimuth and elevation. In that manner, theencoders 41 and 42 transmit the true azimuth and elevation angles fordirect comparison with the azimuth and elevation commands regardless ofwhether the gun is level.

A suitable coordinate converter 60 will now be described with referenceto FIGURES 2, 3 and 4. In order to device a coordinate converter whichis both inexpensive and reliable, the coordinate converter 60 isconnected directly to the gun deflection pintle 61. Since the deflectionaxis 62 does not intercept the axis of elevation, which is the axis ofthe gun trunnion 63, it is necessary to first translate the elevationaxis to a position which does intercept the deflection axis. This isaccomplished by providing a first pulley 64 (FIGURE 2) on the guntrunnion and a second pulley 65 on the deflection pintle 61 with theaxis of the second pulley 65 intercepting the deflection axis 62. A tautband 66 will cause the elevation of the gun about the trunnion axis 63to be translated to the pulley 65. A third pulley 67 and a second band68 translates the gun elevation axis down to the coordinate converter69.

In the coordinate converter 60 illustrated in FIGURES 3 and 4 a firstgimbal-like member 71 maintains the axis of rotation of the pulley 67perpendicular to the deflection axis 62 so that as the pintle 61 rotatesto train the gun in azimuth, the pulley 67 moves in an are about theaxis 62. As the gun is elevated, the pulley 67 rotates about its axis. Asecond gimbal-like member 72 fixedly connected to the pulley 67 iscaused to rotate and thereby move a pin 73 in an arc about the axis ofthe pulley 67 which is parallel to the gun trunnion axis. As the pin 73moves through that arc, a third gimbal-like member 74 is also caused torotate about an axis adjusted to be horizontal by the adjustment of afifth gimbal-like member 75 which holds the axis of a pin 76 at one endperpendicular to the axis of a pin 77 at the other end. The pin 77 isfixedly connected to a leveling. table 78 and the gimbal-like member 75is journaled to rotate about the axis of the pin 77.

Leveling screws 81 and 82 are provided to adjust the leveling table 78about a sphere 83 which is fixed in position on the gun mount 84 withits center on the deflection axis 62. The leveling screws 81 and 82 areadjusted until the axis of the pin 76 is horizontal as indicated by abubble level 85 as shown in the top view of FIGURE 4. Another pair ofleveling screws, not shown in the side view of FIGURE 3, are thenadjusted until the axis of the pin 77 is vertical as indicated by thespirit levels 85 and 86. Once these adjustments have been made, trueazimuth and elevation can be read from encoders 41 and 42, respectively.

In FIGURES 3 and 4, the true elevation and azimuth axis coincide withthe gun deflection axis 62 and the axis of the pulley 67 because the gunis level. Accordingly, motion of the gun in deflection and elevation istranslated directly to the azimuth and elevation position encoders 41and 42, respectively, without conversion. However, this specialcondition will illustrate the manner in which the coordinate converteroperates. As the gun is trained in deflection about the axis 62, the gundeflection pintle 61 will cause the pulley 67 to be moved through an arcof the same angle as the gun deflection. The second and thirdgimble-like members 72 and 74 will then cause the fourth gimbal-likemember 75 to rotate through an arc of the same angle. In that manner,the true deflection of the gun is read directly from the encoder 41. Asthe gun is trained in elevation the pulley 67 causes the pin 73 (FIGURE4) to be moved through an arc of the same angle as the pulley 67. Thatangle is translated by the third gimbal-like member 74 to the elevationencoder 42 so that true gun elevation is read directly.

If the gun trunnion is not horizontal, a trunnion tilt error would existin the output from the encoders 41 and 42 were it not for the coordinateconversion provided by the four gimbal-like members. FIGURE shows thepositions of the first and second gimbal-like members 71 and 72 relativeto the third and four gimbal-like members 74 and 75 after the levelingtable 78 has been adjusted to a true level position by adjusting screws81 and 82 (and two others not shown). As the gun is trained about thedeflection axis 62, the rotation of the gun deflection pintle 61translated through the gimballike members 71, 72 and 74 is converted totrue gun deflection in the rotation of the gimbal-like member 75 aboutthe axis of the pin 77. Similarly, elevation of the gun causes thepulley 67 to rotate about its axis. That rotation is then translatedthrough the gimbal-like members 72 and 74 to the elevation encoder 42 astrue elevation. The gun barrel axis is always parallel to the axis ofthe pin 73 (FIGURE 3) or more properly speaking parallel to the linerunning through the center of the sphere 83 and the pin 73, so that trueazimuth and elevation can at all times be read directly from theencoders 41 and 42, respectively. This is necessarily so because theinner gimbal-like members 74 and 75 are referenced to true vertical andhorizontal axis. Thus connecting the g'u'nbal-like members 74 to the pin73 will allow true gun elevation to be read from the angle between thegimbal-like members 74 and 75 and true azimuth to be read from the anglebetween a reference mark on the leveling table 78 and the position ofthe gimbal-like member 75 or more specifically, the axis of the pin 76.

The reference mark on the leveling table may be adjusted to coincidewith true north, or some other reference point with respect to which theazimuth commands are to be given, by so constructing the leveling tableas to allow the upper half to which the encoder is fixedly attached tobe rotated about the axis of the pin 77.

It is desirable to use fixed ammunition for protecting against weather,and increased rate of fire. In order to use fixed ammunition and havevariable muzzle velocity, the gun breach may be modified to bleed out avariable amount of the powder gasses from the chamber behind theprojectile. A suitable porting arrangement is shown in FIGURES 6 and 7.FIGURE 6 is a section of the gun with a round of ammunition in place. Avariable closure screw 90 is provided to adjust the porting of thepowder gasses according to the muzzle velocity required. As the variableclosure screw is rotated clockwise, it moves along a threaded portion ofthe gun barrel 91 toward the gun breach 92. As shown the variableclosure screw has been rotated counter clockwise sufficiently to open aspace 93 between the closure screw 90 and the breach 92 for maximumporting of the powder gasses and minimum muzzle velocity. The porting ofthe powder gasses is through holes 94 at the base of the gun barrel. Across-section taken along the line 77 is shown in FIGURE 7 to illustratethe pattern of eight porting holes at the base of the gun barrel. Thenumber and size of the porting holes required would depend upon theparticular gun and minimum muzzle velocity desired with a specifiedpowder charge in the fixed ammunition.

As the closure screw is rotated clockwise, the space 93 is decreasedthereby decreasing the amount of powder gasses bled out through theporting holes. A splined sleeve 95 attached to the variable closurescrew is engaged by a gear wheel 96 fixedly attached to a shaft 97 whichis connected to the muzzle velocity encoder 43. In that manner variableporting for variable muzzle velocity can be incorporated in this systemfor accurate transmission of fire control commands between the batteryexecutive officer at a command post and gun crews at remote gunpositions not only for gun laying in azimuth and elevation but also formuzzle velocity.

The indicator 38 (FIGURE 1) is provided to indicate to the gun crew whenthe muzzle velocity setting is too high or too low in the same manner asthe indicator 37 indicates to the gun crew when elevation is too high ortoo low. Once all three position encoders 41, 42 and 43 compare with thecommands in azimuth, elevation and muzzle velocity, and not until then,the gun may be said to be properly laid. Thus the comparator will causethe message coding control unit 45 to transmit an on target message fromthe gun position to-the battery command post only when muzzle velocityis properly adjusted in this manner. If the powder charge is variedinstead, the muzzle velocity encoder 43 would either not be provided orelse would be manually set to a value which would correspond to themuzzle velocity provided by the powder charge actually placed in the gunfor the next round.

While a particular embodiment of the invention has been shown, it shouldbe understood that the following claims are not to be limited to itsince many modifications may obviously be made without departing fromthe true spirit and scope of the invention.

What I claim is:

1. In a fire control system including a communication channel fortransmitting fire commands in true azimuth and elevation between abattery command post and a gun crew and means for comparing the actualgun setting in azimuth and elevation with said commands, a coordinateconverter for translating apparent azimuth and elevation derived fromthe actual movement of a gun about its elevation and deflection axisinto true azimuth and elevation, where true azimuth is taken from anarbitrary reference point, comprising means for translating the axis ofthe gun in elevation to a position which intercepts the axis ofdeflection in azimuth,

a first gimbal-like member coupled to the gun deflection mechanism forrotating said translated elevation axis about said axis of deflection inresponse to training said gun in azimuth,

a second gimbal-like member for rotating a third axis about saidtranslated elevation axis in a plane passing through said axis ofdeflection,

a third gimbal-like member connected to said second gimbal-like memberat said third axis, said third gimbal-like member being constrained torotate about an axis in the same plane as the translated elevation axis,

a fourth gimbal-like member connected to said third gimbal-like memberto restrain the axis of rotation of said third gim'bal-like memberperpendicular to a vertical axis,

leveling means for adjusting said vertical axis to true vertical,whereby training said gun in elevation and azimuth will cause said thirdand fourth gimbal-like members to rotate about the true elevation axisand the true azimuth axis in response to actual movement of the gun,

and angular position transducers connected to said third and fourthgimbal-like members for producing signals indicating the true elevationand azimuth of the gun.

9 10 2. In a fire control system, the combination as dewhereby the anglebetween said second gimbal-like fined in claim 1 wherein member and afixed reference is always equal to the said first gimbal-like member isconnected directly to elevation angle to the gun barrel,

the gun pintle for direct rotation about the deflection means forestablishing a true vertical axis intercepting axis as the gun istrained in elevation, 5 the gun deflection axis at the point ofinterception and said means for translating the gun elevation axis is:between the gun deflection axis and the translated comprised of a firstpulley connected for rotation elevation axis, with the gun trunnionabout the gun elevation axis, a third gimbal-like member mounted forrotation a second pulley connected to rotate said second gimabout saidtrue vertical axis, bal-like member about the translated elevation axis,a fourth gimbal-like member mounted for rotation and a belt system fortranslating angular motion of about an axis perpendicular to said truevertical axis said first pulley to said second pulley, and interceptingsaid true vertical axis where said 3. In a fire control system includinga communication true vertical axis intercepts said gun deflection axis,channel for transmitting fire commands to a gun crew and a pin rotablyconnecting said second and fourth in trueazimuth and elevation and meansfor comparing gimbal-like members at a point along an axis perthe actualgun setting in azimuth and elevation with said pendicular to both theaxis of rotation of said second commands, a coordinate converter fortranslating apgimbal-like member and the axis of rotation of said parentazimuth and elevation of a gun about its elevation fourth gimbal-likemember, whereby: said axis along and deflection axis into true azimuthand elevation, w-here which said pin rotatably connects said second andtrue azimuth is taken from an arbitrary reference point, fourthgimbal-like members is always parallel to the comprising gun barrelaxis; true azimuth of the gun barrel is alfirst means for translatingthe gun barrel elevation axis ways equal to the angle between said thirdgimbalto a parallel position which intercepts the gun barlike member andsaid arbitrary reference; and true rel deflection axis, elevation isalways equal to the angle between said second means for establishing atrue vertical axis and fourth gimbal-like member and a fixed reference.

a true horizontal axis which intercept each other at the same point atwhich the translated elevation References Cited y the Examine! axisintercepts the gun deflection axis, UNITED S T P S a first gimbal-likemember mechanically coupled to the gun for direct rotation in responseto gun deflec- Si et 89-41 emann 89-41 tron of the gun with respect tothe gun carriage 1s 1722 923 7/1929 Just et al. 89-41 always exactlyequal to the angle between the first 2 700106 1/1956 Taylor 89 41 Xgimbal'hke member and a fixed referencc 2j80lj416 8/1957 Evans et al s91 X a second gimbal-like member connected to said first means and saidfirst gimbal-like member with its SAMUELW ENGLE Primal}, Examiner axisof rotation along the translated elevation axis

1. IN A FIRE CONTROL SYSTEM INCLUDING A COMMUNICATION CHANNEL FORTRANSMITTING FIRE COMMANDS IN TRUE AZIMUTH AND ELEVATION BETWEEN ABATTERY COMMAND POST AND A GUN CREW AND MEANS FOR COMPARING THE ACTUALGUN SETTING IN AZIMUTH AND ELEVATION WITH SAID COMMANDS, A COORDINATECONVERTER FOR TRANSLATING APPARENT AZIMUTH AND ELEVATION DERIVED FROMTHE ACTUAL MOVEMENT OF A GUN ABOUT ITS ELEVATION AND DEFLECTION AXISINTO TRUE AZIMUTH AND ELEVATION, WHERE TRUE AZIMUTH IS TAKEN FROM ANARBITRARY REFERENCE POINT, COMPRISING MEANS FOR TRANSLATING THE AXIS OFTHE GUN IN ELEVATION TO A POSITION WHICH INTERCEPTS THE AXIS OFDEFLECTION IN AZIMUTH, A FIRST GIMBAL-LIKE MEMBER COUPLED TO THE GUNDEFLECTION MECHANISM FOR ROTATING SAID TRANSLATED ELEVATION AXIS ABOUTSAID AXIS OF DEFLECTION IN RESPONSE TO TRAINING SAID GUN IN AZIMUTH, ASECOND GIMBAL-LIKE MEMBER FOR ROTATING A THIRD AXIS ABOUT SAIDTRANSLATED ELEVATION AXIS IN A PLANE PASSING THROUGH SAID AXIS OFDEFLECTION, A THIRD GIMBAL-LIKE MEMBER CONNECTED TO SAID SECONDGIMBAL-LIKE MEMBER AT SAID THIRD AXIS, SAID THIRD GIMBAL-LIKE MEMBERBEING CONSTRAINED TO ROTATE ABOUT AN AXIS IN THE SAME PLANE AS THETRANSLATED ELEVATION AXIS, A FOURTH GIMBAL-LIKE MEMBER CONNECTEDD TOSAID THIRD GIMBAL-LIKE MEMBER TO RESTRAIN THE AXIS OF ROTATION OF SAIDTHIRD GIMBAL-LIKE MEMBER PERPENDICULAR TO A VERTICAL AXIS, LEVELINGMEANS FOR ADJUSTING SAID VERTICAL AXIS TO TRUE VERTICAL, WHEREBYTRAINING SAID GUN IN ELEVATION AND AZIMUTH WILL CAUSE SAID THIRD ANDFOURTH GIMBAL-LIKE MEMBERS TO ROTATE ABOUT THE TRUE ELEVATION AXIS ANDTHE TRUE AZIMUTH AXIS IN RESPONSE TO ACTUAL MOVEMENT OF THE GUN, ANDANGULAR POSITION TRANSDUCER CONNECTED TO SAID THIRD AND FOURTHGIMBAL-LIKE MEMBERS FOR PRODUCING A SIGNALS INDICATING THE TRUEELEVATION AND AZIMUTH OF THE GUN.